1. Field of the Invention
The present invention is generally in the field of semiconductors. More specifically, the invention is in the field of semiconductor circuits.
2. Related Art
Mobile phones employing the Global System for Mobile Communication (“GSM”) standard are typically capable of operating in multiple frequency bands. For example, tri-band and quad-band GSM mobile phones are capable of operating in three frequency bands and four frequency bands, respectively, thereby allowing the mobile phone to be used with a variety of service providers, each of which employ a different frequency band.
Current tri-band and quad-band GSM mobile phones have five or six transmit and receive ports, respectively, tied to a common antenna. Each of these ports typically has at least one and sometimes two control lines per port. In the case of a tri-band GSM mobile phone, for example, five or six control lines are typically required in order provide the antenna switching function for its five transmit and receive ports. For the quad-band GSM mobile phone, six or seven control lines are typically required in order provide the antenna switching function for its six transmit and receive ports.
Presently, however, GSM mobile phone chips provide only three or four control lines for the antenna switching function. Conventionally, decoders are used by known antenna switching circuits to reduce the number of control lines from six or seven lines to three or four lines for interfacing with the GSM mobile phone chip. Such decoders, however, occupy significant device area and undesirably increase device size and manufacturing cost. Moreover, the lines which route signals to and from the decoder further consume additional device area and further increase device size and manufacturing cost.
Another disadvantage associated with known antenna switching circuits is the significant DC (battery) current consumed even during standby or “all-off” mode due to the current drawn by known switching circuits through bias resistors connected to the battery. For example, even during standby mode, known antenna switching circuits consume between approximately 10 to 100 microamperes at all times, which is undesirable.
Accordingly, there is a strong need in the art for an efficient multiple-band antenna switching circuit.